The extremely high energy of a lightning strike can cause damage to structures unless adequate protection is provided. Composite structures are particularly vulnerable due to the relatively low electrical conductivity compared to metals. Composite materials are frequently used in aeronautical and aerospace applications due to their high strength to weight ratio and desirably are protected from damage due to lightning strikes.
Traditionally, composite structures were fabricated using hand layup with a conductive layer added manually for lightning strike protection. In order to minimize weight, the lightning strike protection is very lightweight and extremely fragile. Automated methods such as fiber placement and tape laying machines are currently used to automatically fabricate composite structures, however the fragile lightning strike protection is still applied manually.
Lightning protection for composite structures, includes for example, U.S. Pat. No. 3,755,713 issued to Paszkowski, which discloses a metal wire mesh imbedded into a composite structure for lightning strike protection. The metal mesh, foil and/or wires are imbedded into the structure using a manual process.
U.S. Pat. No. 6,692,681 issued to Lunde discloses a method and apparatus for manufacturing composite structures such as an aircraft fuselage. Following fiber-placement of the outer carbon fiber skin, other layers may be manually placed. For example, a fabric layer containing metal filaments for lightning protection may be manually applied.
There is a need for further lightning strike protection for structures, and more particularly to methods for automatically applying lightning strike protection during the forming of structures such as composite structures.